7
You have to set the initial value. In your init try replace with below code.
self.fields['last_name'].initial = last_name
self.fields['my_field'].initial = my_field
The initial can also be passed when the form instance is created.
form = PersonForm(instance=person, initial={'last_name'='Smith', 'my_field'='test123'})
This one is the recommended way to do it. Don’t have to override the init method at all.
Source:stackexchange.com